This invention relates to an automatic engine stop-restart system for automatically stopping an engine under some predetermined conditions, and thereafter, automatically restarting the engine under other predetermined conditions.
In general, during running on a road, when a vehicle has to be stopped for a long period of time because of a traffic jam due to a signal waiting, an accident caused by another vehicle or the like, an engine may be temporarily stopped, and thereafter, restarted after the traffic jam has gone. This is done so as to avoid useless fuel consumption due to an idle operation for a long period of time.
Referring to the running through an urban district, the periods of time for vehicle stopping in the urban district comprises a fairly large percentage of the whole operating time of the vehicle, and the amount of exhaust gases and the quantity of fuel consumed therefor are not neglectable. Therefore, it is conceivable that, upon stopping of the vehicle for the signal waiting and the like during running in the urban district, the engine of the vehicle is stopped by manual operation. However, the stopping of the engine by manual operation each time of the signal waitings leads to the manually engine restarting operation, thereby resulting in a troublesome operation and a delayed starting operation of the vehicle.
There has heretofore been developed an automatic engine stop-restart system wherein, when a motor car is stopped at an intersection or the like during running through an urban district, if it is desirable to temporarily stop the engine for the purpose of improving the fuel consumption rate, the engine is automatically stopped, and thereafter, automatically restarted by a normal starting operation, which is effected at the time of starting the vehicle, such as a depression of a clutch pedal.
In the system of the type described, heretofore, rotation of the engine has been judged only by the level of an output voltage from an alternator, and an automatic stop and restart have been effected based on the result of the judgement. In consequence, there has been a possibility that, if the output voltage from the alternator in level is dropped to substantially zero despite of rotation of the engine, judgement is made that the engine does not rotate, whereby a starter is driven.
On the other hand, in the automatic engine stop-restart system of the type described, a rotational speed of the engine is detected by means of an engine rotation sensor separately of the output voltage of the alternator, and various controls are effected based on the result of the detection. Therefore, when no output is emitted from the rotation sensor due to a trouble therein despite of rotation of the engine, control means judges that the engine is stopped, and the result of the judgement causes a control output corresponding to the engine stopped condition to be fed to various actuators, thus not securing the safety of a vehicle using the system of the type described.